This invention relates to aerosol analyzers, and more particularly, to infrared aerosol analyzers which operate and report results in essentially real time, as events actually occur.
Obtaining accurate measurements of the particle and gas content of the earth's atmosphere and other environments is important to monitor and understand such environments, and changes in the environments. It is useful to chemically characterize and quantify particles of various sizes, such as "ultrafine" particles (less than about 0.3 micrometers), "fine" particles (about 0.3-1 micrometers) and "coarse" particles (about 1-10 micrometers) in the environments, and to measure transient events involving, for example, volatile materials or sequential collections of reactive mixtures containing acidic and basic materials. It is also useful to be able to make field adjustments of the measuring equipment during operation.
Accurate measurements of aerosol samples can be obtained by passing a sample across a series of attenuated internal reflection elements which can be moved at a controlled rate. This has been done in aircraft and other field locations. In known apparatus, particles from the aerosol sample which adhere to the reflection elements are taken to a laboratory for spectroscopic analysis which reveals the chemical nature of the particles. In spectroscopic analysis, infrared light is passed through the reflection elements and analyzed by measuring the frequencies of light which are absorbed by the particles. However, such analyses are not made in "real time", i.e., as events occur, and therefore have limited usefulness for research and other purposes. A problem with this is that a significant amount of time passes between the time the samples are taken and the time the results are obtained. Consequently, inaccurate results are obtained if the sample changes because the collected materials interact. Also, artifact species can be formed during this interim time, and temporal variations in the sampled environment can be missed. Moreover, sample preparation and analysis are time consuming and expensive when using these known methods. Thus, there is a need for methods and apparatus for accurately analyzing the content of atmospheric particulate matter or aerosols and the like in essentially real time.
Accordingly, an object of this invention is to provide new and improved methods and apparatus for analyzing aerosols.
Another object is to provide new and improved methods and apparatus for analyzing aerosols in essentially real time.
Yet another object is to provide new and improved methods and apparatus for analyzing aerosols which reveal temporal variations of an aerosol in essentially real time.
Still another object is to provide new and improved methods and apparatus for analyzing aerosols which reduce artifact formation and reactions of particles with gasses and other particles prior to analysis